In Ethernet networks, several techniques are known for providing network resiliency and self healing functions. These techniques mitigate the effects of communication link or communication equipment failures, and include, for example, Spanning Tree Protocol (STP), Rapid Spanning Tree Protocol (RSTP), Resilient Packet Ring (RPR), and Link Aggregation.
The above mechanisms are typically used by switching/routing nodes to constitute a data path from one user network to another user network based on user-supplied decision parameters. The switching/routing nodes forward traffic in a decided data path until that data path breaks down. When the data path breaks down, a data path is re-established so that user network connectivity is maintained except for the duration of data path re-establishment.
In a wired Ethernet mesh or ring network, the failure of the data path can be recognized by connected nodes either when a response to a transmission by resiliency protocols is not received from an adjacent node within a predetermined time or the nodes identify an explicit failure to receive signals at the physical layer. In a wired network, the second mode of failure results when a physical interface in one or both of the nodes fails or when the interconnecting communication medium, a wire in this case, breaks or disconnects from any node. This type of failure is generally referred to as a symmetrical failure in that adjacent nodes recognize the failure simultaneously and take action to switch traffic to an alternate path very quickly.
In a wireless Ethernet mesh or ring network, however, wireless links are used to interconnect adjacent nodes. A wireless link is different than a wired connection in that there are extra layers of connectivity between the nodes, in the form of radio and physical layers, at each end of the link. There are thus additional potential points of failure in a connection between nodes.
Some types of wireless communication path failures, failures in traffic transfer in only one direction on a wireless communication path due to fading for instance, might not be detected simultaneously in adjacent nodes. Although this type of asymmetrical failure might eventually be detected at both nodes by inherent resiliency protocols, the switchover of traffic to an alternate path, in other words the action by self healing resiliency measures or mechanisms in the nodes, becomes sluggish or very slow and results in data loss over a long period of time. This can also result in a period of time where in the network is in imbalance, causing traffic flooding which affects the performance of traffic in other paths which should not have been affected by failure of a particular path.
Therefore, there remains a need for wireless communication link management techniques which provide for more timely detection of faults or failures. There is also a need for techniques for triggering inherent resiliency mechanisms in switching/routing nodes to act very quickly in re-establishing a data path when a fault or failure has been detected.